December 10 150,000 French troops mass at the border in Vietnam to prevent a Chinese invasion 1949: 150,000 French troops mass at the border in Vietnam to prevent a Chinese invasion. December 10 Japan Becomes Master of the Pacific and South China Sea 1941 On this day, 4,000 Japanese troops land on the Philippine Islands, while Japanese aircraft sink the British warships Prince of Wales and Repulse. Guam, an American-controlled territory, was also seized. British Prime Minister Winston Churchill finally exclaims, "We have lost control of the sea." And the Japanese were far from finished: The humiliation of the United States in the Philippines and a more extensive occupation of Indochina and the South Pacific were still to come.